This invention generally concerns oxidation of halogenated polymers. More specifically, it concerns oxidation of halogenated polymers using acidic oxidizing agents to modify physical and grafting properties of the polymers, and concerns oxidized and graft polymers so prepared.
Known polymer oxidation processes generally involve harsh conditions, which promote degradation and/or crosslinking of polymer chains as evidenced by viscosity changes and molecular weight changes. The oxidized polymers may even become emulsifiable. See, e.g., U.S. Pat. No. 3,329,667 and U.S. Pat. No. 4,156,671. Many of these processes are complex and require numerous preliminary operations to prepare the polymers for oxidation. Such multistep processes are expensive and often make oxidation of prepared and isolated forms of a polymer impractical. Some preliminary steps of multistep oxidation processes involve dissolving or melting the polymer to be oxidized. Loss of polymer is inherent ineach of the steps. Degradation and crosslinking cause additional loss of polymer.
Known polymer oxidation processes are used for hydrocarbon polymers and the like, but are typically not used for halogenated polymers. Oxidative degradation such as that described in Canadian patent 817,505 is, however, sometimes practiced on halogenated polymers. Degradation is evidenced by lowered molecular weight. Additionally, oxygen is sometimes introduced with halogen in processes such as the oxyclorination described in Canadian patent 776,773; however, such processes result in introduction of highly reactive peroxide and hydroperoxide groups, which can lead to instability and degredation.
One object of this invention is to provide an oxidation process suitable for use with halogenated polymers, which causes minimal degredation thereof. Another object of the invention is to provide oxidized halogenated polymers which exhibit modified physical properties.
Yet, another object of the invention is to form graft copolymers of said oxidized polymers by polymerizing monomers or other addition polymerizable compounds in the presence of the oxidized polymers.
Polymers are typically impact modified by being admixed with, being formed in the presence of or being reacted with monomers or polymers known to impart impact strength. Diene polymers such as polymers and copolymers of butadiene are commonly used to impart impact strength. Disadvantages are also experienced with impact modification using diene polymers. Diene polymers typically reduce stiffness or otherwise adversely affect physical properties other than impact properties. Diene polymers also have double bonds which are associated with yellowing on aging or exposure to heat or light. An object of this invention is to prepare impact modified polymers, which have fewer of the disadvantages associated with impact modification using dienes.